Automatic stoker.



aw. SPRAGUE. AUTOMATIC STOKER.

APFLICAHON' I'ILED JAN. 19

Patented. Sept. 18, 191?.

3 SHETS-SHEEF l.

mum/r01? I ATTORNEY E. w SPRAGUE. AUTOMATIC STOKER.

APPLICAHON FILED JAN. l9. i918.

Patentedbvpt. 18, 1917.

3 SHEETS--SHEET 2.

l/Vl/E/VTOR a fl ATTORNEY E. W. SPRAGUE.

AUTOMATHJSTOKER APPLICAHDN HLED JAN. 19. 1915.

1,240,614. PatentedSept. 18,1917.

3 SHEETS-SHEET 3.

IN VEN TOR l/ j y Y ::1- 7

UNITED STATES PATENT OFFICE.

EDWARD W. SPRAGUE, OF ALLEN'TOWN, PENNSYLVANIA.

AUTOMATIC STOKER.

Specification of Letters Patent. Patented Sept, 18, 1917,

Application filed January 19, 1916. Serial No. 72,879.

matic Stokers, of which the following is a specification.

My invention relates to a stoker of the under-feed forced draft type, in which the aim is to secure practically smokeless combustion of the fuel, a great range of capacity, quick response to meet overloads, and a correspondingly high efficiency for all rates of combustion. By my invention various improvements of construction are provided, for the purpose of increasing the range and efficiency of operation, and control of all parts of the moving grate surface, so as to permit the burning of practically all grades of bituminous slack.

As a brief description of various features of my invention it may be stated that coal which is forced by the usual reciprocating plunger or equivalent device into the plunger chamber continues into a movable feeder-duct, having an adjustable movement of reciprocation independent of that of the plunger. By means of and through the movable feeder-duct the coal is forced upwardly and rearwardly into the furnace and onto the grate surfaces. This movable feederduct distributes the fuel in the furnace, agitates the fuel bed and thus prevents clinker formation, and prevents clogging of the fuel between the reciprocating plunger and the furnace. The movable feeder-duct (of whicha number may be employed, driven from one main shaft) carries at its upper end various finger grate bars. upon which the fuel moves and by which it is distributed onto the lower or inclined grates. The finger-bars referred to, constituting the upper or feeder section of the grate surface comprise members formed in such manner as to provide a protecting grate surface for the movable feeder-duct, while providing a means for distributing air to the fuel. and while preventing sifting of fuel into the air chamber beneath. The lower grate section, onto which the fuel is forced by the finger grate bars, consists of moving and stationary grates arranged alternately and set at a slight inclination, the movement of the moving grates producmg a positive movement of the fuel bed, toward the dump plate, which is arranged beyond the grates referred to.

My invention further provides an ashpusher and a dump plate, so arranged that a continuous automatic discharge of ash may be obtained in which the rate of discharge can be varied by adjusting the stroke of the ash-pusher and also the angle of the ash plate. A regulated supply of air is provided by forced draft and natural draft,

the arrangement being such that as the fuel passes the end of the movable feeder-duct, it is thoroughly mixed with air, and as it approaches the incandescent fuel line above the volatile matter is distilled.

The object of my invention is to provide an improved device of the character above referred to, of a simple and durable design, as will appear more fully in the following specification and appended claims.

In order that a clearer understanding of my invention may be had, attention is hereby directed to the accompanying drawings forming part of this application and illustrating certain embodiments of my invention. In the drawings, Figure 1 represents a vertical longitudinal section through a furnace equipped with my invention, Fig. 2 is a front elevation of the same, Fig. 3 is afvertical transverse section taken on line 3-3 of Fig. 1, and Fig. 4 is a detail side elevation of one of the movable inclined grate bars.

1 Referring to the drawings, the furnace 1 is provided with the hoppers 2, 2, through each of which the fuel drops into a cylindrical plunger chamber 3. The fuel is forced forward in each chamber 3 by means of a reciprocating plunger 4, the plungers being reciprocated by connecting rods 5, each of which is pivoted to a plunger at 6 and to a crank pin 7 connected between a pair of disks 8, 8, on the main shaft 9, shaft 9 extending transversely in front of the furnace as shown. As is shown in Fig. 2, the crank pins 7 for a pair of plungers may be arranged 180 apart in relation to main 'shaft 9, the other operative connections to shaft 9 likewise being equally spaced about the shaft, so as to evenly distribute the load upon the shaft throughout the revolution of the same. Shaft 9 is shown as mounted in bearings 10.

A pair of movable feeder-ducts 11, 11, are shown, each feeder-duct being provided at its forward end with'a cylindrical sleeve portion 12 adapted-to slide back and forth on the rear endof the cylindrical plunger chamber 3. Secured to the sleeve 12 is a main portion 13 of the feeder-duct which has an upwardly and rearwardly inclined bottom surface 14, the slope of which be gins at or about a point 15 at which point the cross-section of the duct merges from circular to rectangular, the rear portion of the duct having vertical side walls 16, 16 as is shown in Fig. 3. Each duct is provided adjacent to its rear end with a lug 16 secured to a horizontal plate 17 supported on roller 18 mounted in bearings 19.

A pair of alined rock-shafts 20, 20, are provided each of which has secured thereto a pair of upwardly extending rocker arms 21, 21 and 21, 21'. Each rocker-arm is rocked from main shaft 9 by a connecting rod 22, pivotally connected at one end to a crank pin 23 mounted on a disk 24, on shaft 9, each rod 22 being pivotally connected on its other end to a rocker-arm, as shown at 25, whereby the rocker-arms 21 and 21 will be oscillated, preferably through a loose connection, as will be explained. Each rocker-arm 21 and 21' has a link or rod 26 pivotally secured at one end on a pin 27, mounted between a pair of forked arms at the upper end of the rocker-arm. The other or rearend of each link 26 is pivotally secured toa lug 28, secured to or integral with the horizontal frame member "17 of the feeder-duct.

The reciprocating movement of each feeder-duct thus derived is preferably made variablein length, to suit difierent conditions of operation. This is preferably accomplished in the manner shown in Figs. 1 and 2, in which latter figure it is seen that connecting rod 22 has one end journaled on pin 23, and its opposite end forked and provided with pin 25. A rocker-arm 29 has its upper end pivoted on pin 25, arm 29 having a hub 30 loose on its shaft 20. Rocker-arm 21' or 21, adjacent to arm 29, carries a frame 32, having a rear portion 32 extending behind arm 29, and a forward portion which has a screw-threaded opening therein, in which is mounted a stroke-adjusting screw 31. The end of screw 31 forms an abutment against which the forward side of arm 29 strikes, oscillation being imparted to arm 27' and shaft 20 through abutment 32' and screw 31, the stroke of the feeder duct being varied in accordance with the position of screw 31. In the arrangement shown, for two feeder-ducts, there are two shafts 20,

each having one arm 29 loosely mounted thereon, and two arms, 21, 21, in one case, and 21, 21, in the other case, fixedly secured thereon.

The finger-bars forming the upper section of-the grate surface will now be described. These finger grate bars are plain cast iron pieces with ribs cast on the same in such a manner that air can have free access to the coal, while at the same time coal will not be allowed to sift into the air chamber below. These finger-bars comprise a series of front bars 33, considering the left of Fig. 1 as the front, these bars being secured to the top of member 13 of the movable feederduct, immediately in front of the discharge opening 34 of the feeder-duct, the fingerbars being secured in position by clamps Each bar is provided with a horizontal top flange 36 and a vertical flange 37 provided with lugs 38 on each side, so as to provide openings 39 between the same. The finger-bars 33 being placed side by side horizontally as shown in Fig. 3, a complete opening or air passage 39 is formed half in one bar and half in the adjacent bar. Openings 39 are preferably inclined, as shown in Fig. 1, first downwardly and then upwardly, so that air in space 40 in front of bars 33 may freely pass through openings 39 into the fuel bed, while the fuel cannot readily pass through the openings into the space 40, which space communicates with or is part of the air chamber.

The finger-bars between a pair of adjacent feeder-ducts 14, 14 are shown at 41, 41. These comprise cast iron bars similar to the bars 33 already described, one set of bars being secured by a member 42 to the side wall 16 of one feeder-duct and the other set of bars being similarly secured to the adjacent side 16 of the other feeder-duct. The two sets of bars 41 together have a curved upper surface which acts as a grate surface, the air passages 43 being formed in the sides of adjacent bars in the same manner as was described in connectionwith the series of bars 33, so that air from the space 44 between the feeder-ducts may pass through openings 43 into the fuel bed, while the fuel cannot readily pass downwardly through these openings into the air chamber. Metal sheets 45 are secured in position between the abutting inner edges of the two sets of bars 41, 41, so as to prevent sifting of fuel through the space between these bars, plates 45 being secured to a stationary member 46.

Side finger-bars 47, 47, similar to bars 41 are mounted on the outer side walls of the feeder-ducts and move in engagement with bent plates 48, 48, secured to the side plates 49 secured on the side walls of the furnace structure between which the feeder-ducts are mounted, plates 48 preventing sifting of the fuel on the outer sides of the feederducts. Finger-bars 47 are provided with tortuous 0r inclined air openings in the same manner as bars 41, bars 41 and 47 all extending transversely of the feeder-ducts while bars 33 are mounted longitudinally of the feeder-ducts as shown.

Rear or extension finger-bars 50 are mounted at the rear end of each feeder-duct parallel to the front bars 33, bars 50 being provided with air passages 51 extending through the same, communicating with the air chamber. Bars 50 are secured to an extension 59, of the frame portion 17 of each feeder-duct, the upper surfaces of bars 50 being provided with horizontal flanges 53, forming a part of the upper grate surface in substantial alinement with the upper surfaces of the central bars 41. The rear endsof bars 50 reciprocate above the upper or forward ends of the lower section of grate bars.

The lower, grate bars of the furnace onto which incandescent fuel is fed from the upper grate bars or finger-bars comprise stationary and movable inclined bars ar ranged alternately, one of the stationary bars being shown at 54 and a movable bar at 55. All these bars have a slight downward inclination toward the rear or ash-pit end, stationary bars 54 being supported on frame members 56 and 57. Movable bars 55 are each supported at their lower or rear ends by a rocker 58, the upper or forward end of each bar 55 being supported on a plate 59 supported on an eccentric 60 on a transverse shaft 61 which is continuously rotated by a chain or belt 62 passing over a pulley 63 on shaft 61 and a corresponding pulley on the main drive shaft 9. Accordingly, the movable grates 55 are given a slight elliptical motion, whereby the bed of fuel is given a positive movement toward the dump plate.

' The dump plate 64 is pivoted at 65 underneath the ash-pusher 66 which is pivoted at its upper end at 67 underneath the bridge wall plate 68 of the furnace. The ashpusher has a downwardly extending arm 69 to which is pivotally connected the link 70, the forward end of which is adjustably connected with a rocker-arm 71 secured on the sleeve 30 mounted on rock-shaft 20 and accordingly oscillating with rocker-arm 29. The stroke of the ash-pusher 66 may be adjusted because of the fact that the forward end of rod 70 is threaded and carries a nut link connection 74 extending from the forward end of ash-plate 64, the chain constituting the forward portion of this connection winding about a shaft 75 which may be provided with a hand-wheel 76 and a ratchet and pawl 77 and 78 to hold the same in adjusted position. The discharge of ash can be caused to take place at any desired rate by adjusting the stroke of pusher 66 and the angle of inclination of plate 64 over which the ashes are'forced.

An air chamber 79 extends under the feeder section of the grate, that is to say, under and around the movable feeder-ducts. From this chamber the air passes as described through the openings in the various series of finger-bars 83, 41 and 50, into the fuel bed. 1 The air supply pipes can be attached either to the sides or bottom of this chamber, an air supply pipe being shown at 80 in the drawings. In this connection it may be noted that the top flanges 36 of finger-bars 33 are preferably provided with lugs 81 slidably engaging springs 82 secured to the horizontal wall plate 83 of the furnace, to prevent sifting of fuel above the finger-bars 33, into the air space 40.

A second air chamber 84 is located under the grates 54 and 55 being separated from air chamber 79- by a partition 85. damper 86 is placed in this partition, and is adapted to be operated by a rod 87 having a handle 88 in front of the furnace, so that forced draft may be used under grates 54, 55, when desired, by opening damper 86. Ordinarily, however, natural draft only will be used under grates 54 and55 and for this purpose a pair of dampers 89 are positioned to govern openings in the bottom of chamber 84, these dampers 89 being positioned by a link 90 having a handle 91 in front of the furnace.

The operation of my improved device will now be clear. Coal forced rearwardly into the plunger chambers and movable feeder-ducts, by plungers 4, is forced upwardly and rearwardly, as the feeder-ducts reciprocate, onto the finger-bars 33, 41, 47 and 50, the coal piling up on these bars and between the central and side bars 41 and 47. From the feeder-bars the coal gradually moves onto grate bars 54 and 55, combustion occurring above both the fingerbars and the lower grate-bars. It will be observed that the feeder-ducts are separately operated from shaft 9 in such manner that the required power may be distributed throughout the revolution of the main shaft. The feeder-ducts perform the functions of conveying fuel to the furnace and distributing fuel therein; and of preventing clogging of the fuel between the plungers 4 and the furnace, because of the movement of the feeder-ducts and the inclined surfaces 14 thereof. The feeder-ducts also agitate the fuel bed, because of their movement, and prevent clinker formation.

The finger-bars locatedabove and movable with the feeder-ducts provide a protecting grate surface for the feeder-ducts and also provide means for distrlbuting air to the fuel. They also act, in combination with the feeder-ducts, as fuel distributers, and also serve to prevent sifting of fuel into the air chamber beneath. The functions of the lower grate bars 54 and 55 are to agitate the fuel bed and force the same toward the ash plate, and to prevent formatlon of clinkers in the lower end of the furnace, by the movement of bars 55. These grate bars are also arranged to allow free access of air to the fuel.

In general, it should be noted that when the fuel passes the upper end of the feederducts it is thoroughly mixed with air, and the volatile material is distilled as the fuel approaches the incandescent Zone above the feeder-ducts. A smokeless operation is assured because of the consumption of the volatile matter as it passes through the fire zone. An intense heat uniformly distributed over the entire grate surface, wlthout any blow-pipe effect, is the result of the described construction. The incandescent fuel is forced slowly toward the rear, and when the rate of operation and air supply are properly regulated, the fuel should be completely consumed as it reaches the ash plate.

It should be noted that my invention is not strictly limited to the exact details of construction, but is as broad as is indicated by the accompanying claims.

Having now described my invention, what I claim as new therein and desire to secure by Letters Patent is as follows 1. In a furnace, the combination of a fuelreceiving chamber, a feeder-duct in allnement, and forming a continuous passage, therewith, said duct having an upwardly and rearwardly sloping bottom, a grate surface carried by said duct, extending alongside the side edges, in front of, and to the rear of, the rear delivery end of said duct, the grate surface across the front of said delivery end extending upwardly above the plane of the side and rear grate surfaces, means for advancing fuel from said chamber into said duct, and means for reciprocating said duct, substantially as set forth.

2. In a furnace, the combination of a fuelreceiving chamber, a feeder-duct in alinement, and forming a continuous passage, therewith, said duct having side walls and an upwardly and rearwardly sloping bottom, terminating in a delivery opening in an approximately horizontal plane, a feedergrate carried by said duct, comprising bars extending at the sides of the opening and across the front edge of the opening, means for advancing fuel from said chamber into said duct, means for reciprocating said duct, and an inclined grate, receiving fuel from said feeder-grate, substantially as set forth.

3. In a furnace, the combination of a feeder-grate, a lower grate, means for moving fuel gradually onto said feeder-grate, and thence onto said lower grate, a forceddraft chamber under said feeder-grate, a natural-draft chamber under said lower grate, a partition separating said chambers, a damper controlling an opening in said partition, and a damper controlling an opening in a wall of said natural-draft chamber, to

- permit the use of natural draft under said lower grate when said first-named damper is closed and said last-named damper is open, substantially as set forth.

4. In a furnace, the combination of a reciprocating feeder-duet, having an upwardly extending delivery end, a grate carried thereby, comprising grate bars positioned about the delivery opening, said bars comprising parallel bars extending forward from the forward edge of the opening, and parallel bars extending at the sides and in the rear of the rear edge of the opening, and a rear grate, said rear reciprocating bars moving over and delivering fuel to the forward end of said rear grate, substantially as set forth.

5. In a furnace, the combination of a reciprocating feeder-duct, having an upwardly extending delivery end, a grate carried thereby, comprising grate-surfaces extending at the sides and across the front of the opening, the grate at the front extending above the plane of said side grate surfaces and being adapted to push rearwardly fuel positioned to the rear of the same, means for progressing fuel through said duct, and an air-chamber, said front and side grate surfaces having air passages therethrough, communicating with said air-chamber, said passages being inclined to prevent the sifting of fuel therethrough, substantially as set forth.

6. In a furnace, the combination of a pair of parallel feeder-ducts, having upwardlyextending adjacent delivery ends, means for reciprocating said ducts, one in advance of the other, means for progressing fuel into the same, grates carried by said ducts, upon the adjacent inner sides of said. delivery ends and across the front of, and to the rear of, said ends, the grates at the front having approximately vertical rear edges extending above the plane of said side grates and being adapted to push rearwardly fuel positioned to the rear of the same, substantially as set forth.

7. In a furnace, the combination of a feeder-grate comprising forward and rear and side series of grate-bars arran ed about sitioned to the rear of the same, substantially an opening, under-feed means for elivering as set forth. 10 fuel through said opening, and means for This specification signed and witnessed reciprocating said grate, the grate-bars this 31st day of Dec., 1915.

across the front of the opening having ap EDWARD W. SPRAGUE. proximately vertical rear edges extending Witnesses: above the plane of said side grate-bars and FRANCIS K. HOWELL,

being adapted to push rearwardly fuel po- GUY P. SHAMRO- 

